1,721,270 research outputs found
Invisible defects in complex crystals
No full textWe show that invisible localized defects, i.e. defects that cannot be
detected by an outside observer, can be realized in a crystal with
an engineered imaginary potential at the defect site. The invisible
defects are synthesized by means of supersymmetric (Darboux)
transformations of an ordinary crystal using band-edge wavefunctions to construct the superpotential. The complex crystal has an entire real-valued energy spectrum and Bragg scattering is not influenced by the defects. An example of complex crystal synthesis is presented for the Mathieu potential
Anyonic Bloch oscillations
No full textThe onset of Bloch oscillations (BOs) for two correlated anyons hopping on a one-dimensional lattice is theoretically investigated in the framework of the anyon-Hubbard model. It is shown that, even in the absence of on-site particle interaction, BOs are degraded for a nonvanishing statistical phase exchange owing to the nonlocal quasiparticle nature of anyons. A remarkable exception is found for pseudofermions, i.e., particles that, although they are bosons on site, behave as fermions off site. In this case, if the ratio of forcing to the hopping rate is smaller than ∼0.5, in the absence of on-site interaction long-lived BOs are observed at a frequency which is half the BO frequency of single particles. This is notably distinct from results for previously investigated BOs of two strongly correlated bosons or fermions, in which particle correlation leads to a doubling of the BO frequency
Tamm–Hubbard surface states in the continuum
No full textIn the framework of the Bose–Hubbard model, we show that two-particle surface bound states embedded in the continuum (BIC) can be sustained at the edge of a semi-infinite one-dimensional tight-binding lattice for any infinitesimally-small impurity potential V at the lattice boundary. Such thresholdless surface states, which can be referred to as Tamm–Hubbard BIC states, exist provided that the impurity potential V is attractive (repulsive) and the particle–particle Hubbard interaction U is repulsive (attractive), i.e. for UV < 0
A time-periodic PT -symmetric tight-binding lattice Hamiltonian: spectral properties and transport features
No full textWe investigate the spectral properties and dynamical features of a time-periodic PT -symmetric Hamiltonian on a one-dimensional tight-binding lattice. Our analysis shows that a high-frequency modulation can drive the system under a transition between the broken-PT and the unbroken-PT phases. Interestingly, the time-periodic modulation in the unbroken-PT regime results in novel spectral features and transport behavior, with no counterpart in Hermi- tian time-periodic lattices. In particular, a significant broadening of the quasi-energy spectrum is predicted, leading to a hyper-ballistic transport regime. Also, near the PT -symmetry break- ing the dispersion curve of the lattice band becomes linear, with a strong reduction of quantum wave packet spreading
Integrated fiber-coupled launcher for slow plasmon-polariton waves
No full textWe propose and numerically demonstrate an integrated fiber- coupled launcher for slow surface plasmon-polaritons. The device is based on a novel plasmonic mode-converter providing efficient power transfer from the fast to the slow modes of a metallic nanostripe. Total coupling efficiency with standard single-mode fiber approaching 30% (including ohmic losses) has been numerically predicted for a 25-μm long gold-based device operating at 1.55 μm telecom wavelength
Floquet-Hubbard bound states in the continuum
No full textWe theoretically demonstrate that a type of robust two-particle bound state embedded in the continuum
(BIC), which we call Floquet-Hubbard (FH) BIC, can be induced in a homogeneous (i.e., defect-free) Hubbard
semilattice by an intense oscillating electric field. While single-particle BIC states are fragile states that exist
solely for specially tailored potentials, FH BIC states are found in a wide range of parameter space, do not require
fulfillment of resonance conditions, and are thresholdless. Analytical results are derived in the high-frequency
limit of field modulation by a multiple-time-scale asymptotic analysis of the ac-driven Hubbard Hamiltonian in
the two-particle sector. A FH BIC mode basically corresponds to a molecular state, in which the two particles
bind together, undergoing correlated tunneling on the lattice. Localization of the molecular state is induced by
the external oscillating field, which effectively attracts the molecular state at the edge of the semi-infinite lattice.
Our results can pave the way for the study and interpretation of strong-field phenomena in correlated-particles
physics
Absence of Floquet scattering in oscillating non-Hermitian potential wells
No full textScattering of a quantum particle from an oscillating barrier or well does not generally conserve the particle energy owing to energy exchange with the photon field, and an incoming particle-free state is scattered into a set of outgoing (transmitted and reflected) free states according to Floquet scattering theory. Here we introduce
two families of oscillating non-Hermitian potential wells in which Floquet scattering is fully suppressed for any energy of the incident particle. The scattering-free oscillating potentials are synthesized by application of the Darboux transformation to the time-dependent Schroedinger equation. For one of the two families of scattering-free
potentials, the oscillating potential turns out to be fully invisible
Correlated super-Bloch oscillations
No full textThe coherent dynamics of two strongly interacting electrons hopping on a one-dimensional lattice and driven by combined dc-ac fields is theoretically investigated in the framework of the Hubbard model. It is shown that, under appropriate forcing conditions in the strong-field regime, super-Bloch oscillations (SBOs) can be observed for the bound particle state, but not for unpaired electrons that remain frozen in the lattice. As compared to single-particle SBOs, SBOs of correlated particles are generally quasiperiodic
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